Get a container and an air valve. drill a hole about 1/2" above the bottom. Install air line tubing in with silicone and put your valve on. drain your water through this hose. Not my Idea. stole it from an existing model on the market.. I will never tell you who though..
Do you mean how to siphon out the kalkwasser
during the initial mixing? if so...
after 3-4 hrs siphon the middle of the mixing kalk by first filling up a siphon tube with water-plug the end---insert into middle and let it flow!